This invention concerns a method for the production of pre-mixed porous polymer compositions, particularly though by no means exclusively suitable for use in the formation of impact absorbing surfaces or substrates for sports or childrens' play areas. Known such impact absorbing surfaces comprise granules of natural synthetic rubber, such as SBR and EPDM for example, in a matrix of polymer, such as polyurethane for example. The matrix may completely fill the spaces between the granules to give a non-porous composition of may simply coat the surfaces of the granules to cause them to adhere leaving the interstices between the granules void to give a porous product.
Either kind of composition may be laid to form a sports or play surface or to form a substrate to another surface such as that provided by synthetic turf for example.
The compositions are prepared on site immediately before installation by accurately metering out the granules, liquid pre-polymer and, if necessary, a catalyst and thoroughly mixing them prior to laying in the manner of asphalt.
The on-site preparation necessitates the use of mixing equipment and trained operators regardless of the size of the project. It would be desirable to eliminate the need for accurate on-site metering of constituent materials and thorough mixing thereof by pre-mixing the granule and pre-polymer and storing this mixture for later application. However, attempts to do so have previously been thwarted by unwanted polymerization of the pre-polymer induced at mixing by the presence of moisture on the surface of the granules or curing agents present in the granules and after bagging by the diffusion of atmospheric moisture through the bag walls.
It is an object of the present invention to provide a method for production of a pre-mixed porous composite which overcomes the disadvantages aforesaid.